Marking grids are used during radiographic imaging to provide visual reference points on the radiographic image. For example, marking grids may be used to locate the position of internal body structures or tumors relative to the reference points on the radiographic image. To use a marking grid, the marking grid is placed on or adjacent to the patient's body while the radiographic image is taken. The marking grid creates lines or dots on the radiographic image which can be used as reference points to locate the position of body structures or tumors relative to the location of the marking grid on the patient. Marking grids are often used in computerized tomography (CT) scanning to produce reference points on the CT scan image.
Prior marking grids have been comprised of elongated radiopaque strips or members fixed to a substrate material. The substrate material in these devices has been in the form of sheets, generally without openings in the material. As a result, the making grid must be moved to allow the radiologist to mark the patient's skin or to insert a surgical device such as a biopsy needle. This can require multiple scans of an area to locate the biopsy needle properly.
Some prior marking devices have partially addressed this problem by providing one or more holes for inserting biopsy needles through the marking device. For example, in U.S. Pat. No. 4,860,331 to Williams et al., a marking device is described in which the substrate is perforated with widely spaced, small diameter holes to permit insertion of biopsy needles. These holes are not always in the optimal position for insertion of a biopsy needle, and the holes do not provide an adequate area for a radiologist to place necessary markings on a patient's skin. As a result, the radiologist may have to move the marking grid for insertion of biopsy needles or marking the skin, which can result in inaccurate insertion or marking.
Accordingly, it is an object of the present invention to overcome one or more of the drawbacks or disadvantages of the prior art and to provide a marking grid for radiographic imaging that allows a radiologist to place markings on the patient's body or insert biopsy needles in the optimum desired location selected by the radiologist, and to provide an improved method of making a marking grid.